1. Field of the Invention
The present invention relates to light indicating devices and more particularly to a lamp cap for use with such light indicating devices, particularly when the source of light provided is from a light emitting diode or similar low output light producing device.
2. Description of the Prior Art
The use of indicating light devices or more commonly pilot lights, is well known in the electronics field. Such devices are frequently combined with various switching devices to provide an indication of the off/on condition of the associated switching device. Simple pilot lights are usually employed as indicators of circuit condition (viz: on/off, etc.).
When a number of such indicating devices or switching devices including associated pilot lamps are provided a distinction between one or more indicators or switches must be made, which may take the form of labeling or providing a colored lamp cap over the light indicating device whereby those lamps which are operated are easily recognized and distinguished from others that may be located in a similar environment. As further means of distinguishing, inscriptions are sometimes included on the top surface of such lamp caps so that an alpha-numeric or similar designation is visible on the top of the lamp cap.
An illuminated push button switch including a light source and including a lamp cap of conventional design is shown in U.S. Pat. No. 3,183,333. Another form of illuminated push button wherein light from a remote source is transmitted by means of a conductive light bar to push buttons to form illumination is taught by U.S. Pat. No. 3,213,269. Such devices require light sources of fairly high output to provide a reasonably high degree of illumination particularly when the indicating devices or switches are employed in an environment where the illumination levels are fairly high.
A particular disadvantage of most prior art indicating lamps and illuminated switching devices is the requirement that a fairly bright incandescent or similar lamp be utilized as the light source. Such incandescent lamps have a fairly short life and also are costly to operate because of their current demands.
Recently light emitting diodes have been utilized as indicating devices in the electronics field, because of their small component size and very low current demands. Such devices however have been of marginal effectiveness, however because of their relatively low light output. Nevertheless, because of their longer life and their resistance to shock and vibration the light emitting diode appears as a desirable light producing device for use in light indicating devices and similar applications. Accordingly it is the object of the present invention to provide a lens for use with light indicating devices employing light emitting diodes as the source of illumination, which concentrate the limited light available from a light emitting diode into a form where it is readily visible even in highly illuminated environments.